Total joint replacement (TJR) (also called primary total joint arthroplasty) is a surgical procedure in which the articulating surfaces of a joint are replaced with prosthetic components, or implants. It is a successful procedure, especially for hips, knees, shoulders, and ankles and allows people to restore functionality while greatly reducing pain associated with osteoarthritis.
Bone is a living tissue that is constantly changing through the resorption of matrix by osteoclasts and the deposition of new matrix by osteoblasts. Articular cartilage is an avascular tissue that is found on the surfaces of joints and serves to provide a smooth interface upon which bones can articulate with each other. Joint replacement arthroplasty is an orthopedic procedure in which the typically worn surface of the joint is replaced with a prosthetic component, or implant. Joint replacement arthroplasty typically requires the removal of the articulating cartilage surface of the joint including a varying amount of bone depending on the joint and the replacement implant being used. The articulating cartilage surface and bone is then replaced with a synthetic, typically metal implant that is used to create a new joint surface.
The correct placement of the femoral and tibial components in total knee arthroplasty has a direct impact on clinical outcomes and implant longevity. One particularly difficult placement parameter is the internal-external rotation of the tibial component on the tibia. Rotational malpositioning of the femoral or tibial component may result in flexion instability, component wear, deviated patellar tracking, and inadequate unsatisfactory joint kinematics, and pain.
During a conventional total knee arthroplasty, either with manual instruments or via computer navigation, a tibial trial component is used prior to implantation of the final tibial component. The tibial trial component is used to verify the size of the final component and to ensure the desired flexion-extension gap and ligament balancing has been achieved. To determine the correct internal-external rotation of the final component, two methods are commonly used. One method references an anatomical landmark whereby the component is aligned with the midsulcus of the tibial spine, the posterior condylar line of the tibia, the medial border of the tibial tubercle, or the medial ⅓ of the tibia tubercle. Another method allows the tibial trail to freely rotate throughout flexion and extension. The component is then aligned with the anterior position of the trial in extension and another reference point (e.g., center of tibia, posterior cruciate ligament (PCL)) on the tibia. However, clinical studies have shown that the final internal-external rotation of the component has a large patient intervariability using either method. In the first method, the tibial trial is fixed to the tibial plateau, making it difficult to determine the best axial rotation of the component. The anatomic landmarks used to identify the correct internal-external rotational alignment are also difficult to locate intraoperatively. The second method lacks in assessing the full range of internal-external rotation throughout flexion-extension.
Additionally, during knee arthroplasty, the posterior slope of the tibial cut is determined prior to using the provisional component, which makes it difficult to determine how much adjustment, if any, is needed in this degree of freedom. The final posterior tibial slope can have a significant impact on clinical outcomes, joint stability, joint kinematics, and implant longevity. Traditionally, the surgeon will try to restore the patient's natural slope and use a provisional component to ensure the ligaments are balanced. In some circumstances, the slope needs to be re-cut after the trial has been used, and the degree of angulation is determined based on the surgeon's judgment. However, because the tibia has already been cut, it can be difficult to determine how much angulation, if any, is needed when performing a recut of the tibia.
Therefore, there is a need for a tibial trial component that can assist a surgeon in consistently placing the final tibial implant component in the proper internal-external rotation. There is an additional need for a tibial trial component that can provide a surgeon with a quantitative measurement of a posterior tibial slope re-cut. There is a further need for a method to mark or assist with the proper positioning of the final component as determined by the tibial trial.